Recently got the engine management light on the motorway, and found out it was from the p0430 message, which indicates a dodgy catalytic converter.

Got a trite confused though because it seems my jag model only has upstream o2 sensor values - bank 1 and bank 2 only have one set of values each, and these display the typical sine wave style results. Surely any downstream o2 results should be picked up by the obd2?

I even compared that torque android app with the results from the Gendan engine check pro equipment.

Question is, have I completely misunderstood the results somehow?
I haven't stuck my head under the bonnet to double check that the cats actually have their downstream o2s BTW.

 

Without even looking it up it is almost assured that your model year has the down stream sensors.

 

The downstream sensors are sometimes referred to as CATALYST MONITORS.
They might also be listed as B1S2, B2S2.

bob gauff

 

If the sensors read "in range", but the results between the two sensor readings are not "normal" you could (and apparently sometimes do) get the catalytic fault due to a bad sensor. The service manual even lists "catalyst failure" as the last entry in "possible causes"!

 

I might be having a "magic moment" which isn't unusual.

Although, there is a lot of wood getting in the way of the trees too :-)

Here's a list of results from the Gendan equipment:
Time
Calculated Load
Coolant Temperature
Short Term Fuel Trim (Bank 1)
Long Term Fuel Trim (Bank 1)
Short Term Fuel Trim (Bank 2)
Long Term Fuel Trim (Bank 2)
Engine RPM
Vehicle Speed
Ignition Timing Advance
Intake Air Temperature
Air Flow Rate (MAF)
Absolute Throttle Position

Oxygen Sensor 2 - Bank 1 voltage
Oxygen Sensor 2 - Bank 2 voltage
Oxygen Sensor 1 - Bank 1 (Wide band) Equivalence Ratio
Oxygen Sensor 1 - Bank 1 (Wide band) Current
Oxygen Sensor 1 - Bank 2 (Wide band) Equivalence Ratio
Oxygen Sensor 1 - Bank 2 (Wide band) Current

Battery voltage
Fuel System 1 Status
Fuel System 2 Status

I was expecting to see:
Oxygen Sensor 1 - Bank 1 voltage
Oxygen Sensor 1 - Bank 2 voltage
Oxygen Sensor 2 - Bank 1 voltage
Oxygen Sensor 2 - Bank 2 voltage

All ideas welcome, as I head out to investigate the bits under the bonnet :-)

Chris

 

Ok, I think you meant to post the actual readings, but they didn't come through. Anyway, I believe I can shine just a little light on your "mystery". The AJ27 engine, which you have in a MY01 XJ8 uses wideband lambda sensors in the precat position. They normally do not cycle the same way as the "standard' zirconium sensors and give a more linear response to lambda values. So, the resulting parameters need to be analyzed differently and are reportd as separate PIDs.

 

Sparkenzap, now that does make sense.
I guess that makes all my recently acquired knowledge on how O2 sensors work, pretty null n void? Uh.

Have attached the Engine Check Pro results to this post.
The Sensor 1's are all "Wide Band" in the graph (in mA), and the sensor 2's are both in voltage.

Can I work out whether the cat is looking a bit tired from the values posted?
I was expecting to see a flat/steady line post cat...

Chris

 

Just read up on the net about the two main types of sensor. The widebands cost more but allow better engine control (fuelling). There's no adequate cost justification to have them as downstreams, though.